Compact ultrasonic flowmeter

ABSTRACT

A compact ultrasonic flowmeter for measuring flowrate and other fluid related data of a fluid includes a flow tube with a flow bore for passage of the fluid between an inlet and an outlet, a flowmeter housing, a printed circuit board arranged in the flowmeter housing and including a processor for controlling operations of the flowmeter, a meter circuit including ultrasonic transducers provided on the printed circuit board and configured for operating the ultrasonic transducers to transmit and receive ultrasonic wave packets through the fluid, a display mounted on the printed circuit board and configured for displaying a measured flowrate and the other fluid related data, one or more battery packs for powering flowmeter operations, and two or more backing devices arranged to provide a holding force to the ultrasonic transducers, forcing a lower side of the ultrasonic transducers against transducer areas provided on the flow tube.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16,376,620, filed Apr. 5, 2019, which claims priority to EuropeanApplication No. 18165942.6, filed Apr. 5, 2018, both of which areincorporated herein by reference in their entireties.

FIELD OF THE INVENTION

The present invention relates to ultrasonic flowmeters for measuringflowrate and other fluid related data, the flowmeters comprising a flowtube and a flowmeter housing containing flowmeter components including aprinted circuit board with surface components on one side.

BACKGROUND OF THE INVENTION

Electronic or steady state flowmeters, such as ultrasonic flowmeters,are increasingly being used as utility meters for measuring waterconsumption. Compared to traditional mechanical flowmeters, anultrasonic flowmeter provides the advantage of having no moving parts.Another advantage is the electronic nature of ultrasonic flowmeters. Asultrasonic flowmeters include a power source for powering themeasurement circuit, often a battery, a radio communication device forexternal communication may also be integrated. Furthermore, ultrasonicflowmeters often include onboard processing capabilities, making dataprocessing available in the meter.

With an increasing focus on environmental issues, including waterscarcity, water metering is on the rise resulting in more meteringpoints on a global scale. Additionally, advancements in sensortechnology and data processing have made it possible to gather new typesof data and to use that data for new purposes, such as leak detection,water quality assessments, etc., rather than just water consumption.With an increasing number of metering points, water metermanufacturability becomes an important factor and even minorimprovements may have a significant impact on the total cost of ametering infrastructure including tenth of thousands of meters. Hence,an improved more compact and manufacturing friendly ultrasonic flowmeterwould be advantageous.

SUMMARY OF THE INVENTION

It is an object of the present invention to wholly or partly overcomedisadvantages and drawbacks of the prior art. More specifically, it isan object to provide a compact and manufacturing friendly ultrasonicflowmeter.

Thus, the above described object and several other objects are intendedto be obtained in a first embodiment of the invention by providing acompact ultrasonic flowmeter for measuring flowrate and other fluidrelated data, comprising: a flow tube with a flow bore for passage ofthe fluid between an inlet and an outlet; a flowmeter housing associatedwith the flow tube; a printed circuit board arranged in the flowmeterhousing and including a processor for controlling operations of theflowmeter; a meter circuit including two or more ultrasonic transducersprovided on the printed circuit board and configured for operating theultrasonic transducers to transmit and receive ultrasonic wave packetsthrough the fluid; a display mounted on the printed circuit board andconfigured for displaying a measured flowrate and other fluid relateddata; and one or more battery packs for powering flowmeter operationsincluding at least the processor and the meter circuit and the display;wherein the processor and the ultrasonic transducers are surface mountedon a lower side of the printed circuit board and the display is mountedon an upper side of the printed circuit board.

By arranging surface mounted devices on one side of the printed circuitboard and through hole components on the opposite side, an effective andreliable manufacturing process may be achieved. Additionally, by fittingelectronic components associated with core flowmeter functionality ontoone printed circuit board, a compact ultrasonic flowmeter is achievable.

In one embodiment, the flowmeter housing may be integrated with the flowtube, e.g. by being cast as a fully integrated monolithic component.Embodiments of the compact ultrasonic flowmeter may also be providedwith a single printed circuit board wherein the processor and theultrasonic transducers are surface mounted on a lower side of the singleprinted circuit board and the display is mounted on an upper side of thesingle printed circuit board.

By integrating the flowmeter housing with the flow tube and fitting allcircuits and electronic components onto a single printed circuit board,a very compact and manufacturing friendly ultrasonic flowmeter isachieved. The compact ultrasonic flowmeter thus comprises only a singleprinted circuit board arranged in the flowmeter housing.

The ultrasonic flowmeter may further comprise a front plate providedwith an opening for receiving a display, and the front plate may bearrange in flush with the display, such as 10-40 mm above the printedcircuit board. Hereby the ultrasonic flowmeter is kept compact.

Additionally, the front plate may substantially cover the printedcircuit board. Hereby the printed circuit board is shielded andprotected by the front plate. The ultrasonic flowmeter described abovemay also comprise a container arranged on top of the printed circuitboard, wherein the container is provided with a through-going opening173 for receiving the display and configured to protect the printedcircuit board and other components mounted thereon.

Moreover, the ultrasonic flowmeter may comprise a radio communicationdevice mounted on the printed circuit board, wherein the radiocommunication device is electrically coupled to an antenna element via aradio circuit, and the antenna element is mounted on the container andreleasably coupled to the radio circuit. Here, the antenna element maybe mounted on a side face of the container.

Additionally, the radio communication device may be configured to detectwhether it is electrically connected to the antenna element and theprocessor may be configured to determine that the container has beenlifted above the printed circuit board based on input from the radiocommunication device, that the electrical connection to the antennaelement has been disconnected.

The ability to determine whether the container has been lifted based ondetection of the antenna element may provide a tamper detectionfunctionality as the container and front plate shields and protects theprinted circuit board including the metering circuit.

Further, the antenna element may be connected to the radio circuit viaconnectors provided on the printed circuit board and/or the antennaelement. Also, the connectors and/or mating connector surfaces may bearranged on the printed circuit board along its periphery, correspondingto the position of the antenna element on the container. Such connectorsmay for example be of the spring contact connector type.

Additionally, the front plate may constitute a lid for the container andthe container may contain a desiccant.

Furthermore, the ultrasonic transducers may be positioned on transducerareas provided on an outer surface of the flow tube, or on an uppersurface of a bottom part of a separate flow meter housing mounted on aflow tube.

In one embodiment of the compact ultrasonic flowmeter described above,backing devices may be arranged on the printed circuit board oppositethe transducers to providing a holding force pressing a lower side ofthe transducers against the transducer areas, i.e. the flow tube. Suchbacking devices may be mounted on top of the printed circuit board toapply the holding force to an area of the printed circuit boardcontaining the ultrasonic transducers. The backing devices may comprisea backing element abutting the transducer and/or the printed circuitboard and a restrained resilient member configured to provide theholding force. Furthermore, the backing device may include a bracketelement arranged to displaceably receive the backing element and theresilient member in the form of a helical spring retained between thebracket element and the backing element. Additionally, a lower side ofthe ultrasonic transducers may be secured to the transducer areas by anon-hardening adhesive, such as a butyl containing adhesive.

Furthermore, the ultrasonic transducers may be mounted on islandsprovided in the printed circuit board being connected with the remainingprinted circuit board via tongues of the printed circuit boardcontaining copper traces for electrically connecting the ultrasonictransducers to the remaining meter circuit. Such design provides acertain resilience to the design and allows limited transducerdisplacement towards the flow tube.

Additionally, the ultrasonic flowmeter may be a utility meter for meterwater consumption or a utility meter for metering fluid flow in a heator cooling meter installation. The ultrasonic flowmeter described abovemay also additionally include a temperature probe for measuring thetemperature of a fluid flowing through the flow tube.

Moreover, the ultrasonic flowmeter may be configured to includeregisters for storing meter data, such as flow-, volume- and/orconsumption data. The ultrasonic flowmeter may also store other meterdata, such as event- or performance data related to the operation of themeter or data related to other sensors (internal of external) connectedto the meter.

The above described embodiments may each be combined with any of theother embodiments. These and other embodiments will be apparent from andelucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE FIGURES

The compact ultrasonic flowmeter according to the invention will now bedescribed in more detail with regard to the accompanying figures. Thefigures show one way of implementing the present invention and is not tobe construed as being limiting to other possible embodiments fallingwithin the scope of the attached claim set.

FIG. 1a shows a compact ultrasonic flowmeter,

FIG. 1b shows a transversal cross-section of an ultrasonic flowmeter,

FIG. 1c shows a longitudinal cross-section of an ultrasonic flowmeter,

FIG. 2 shows a compact ultrasonic flowmeter with an open flowmeterhousing,

FIG. 3a shows the insides of the compact ultrasonic flowmeter,

FIG. 3b shows a longitudinal cross-section of the insides of the compactultrasonic flowmeter,

FIG. 4 shows a printed circuit board of a compact ultrasonic flowmeter,

FIG. 5 shows a desiccant container including a front plate,

FIG. 6 shows a desiccant container without a front plate,

FIG. 7 shows an upper side of a printed circuit board of a compactultrasonic flowmeter,

FIG. 8 shows a lower side of a printed circuit board of a compactultrasonic flowmeter, and

FIG. 9 shows a cross-section of a transducer backing device.

DETAILED DESCRIPTION

FIG. 1 a, 1 b, and 1 c illustrate a compact ultrasonic flowmeter 1according to one embodiment of the invention. The flowmeter comprises aflow tube 11 with a flow bore 111 for passage of the fluid between aninlet 112 and an outlet 113. A flowmeter housing 12 is formed as anintegrated part of the flow tube thereby providing a compartment formeter components arranged at the flow tube to measure the flow rate of afluid flowing in the flow bore. The flowmeter housing is closed-off by alid 121 constituted by a locking ring 122 and a transparent coverelement 124. Between the lid and the flow meter housing a sealingelement 123 is arranged to provide a hermetical seal.

Inside the flowmeter housing a printed circuit board (PCB) 13 includinga processor 135 for controlling operations of the flowmeter is arranged.The PCB further includes a meter circuit (not shown) and two ultrasonictransducers 14 mounted on its lower side 131. A lower side 141 of theultrasonic transducers opposite an upper side connected to the PCB, isarranged against an outer surface of the flow tube 11. The meter circuitis configured for operating the ultrasonic transducers to transmit andreceive ultrasonic wave packets through the flow tube and a fluidpresent in the flow bore. On an upper side 132 of the PCB 13 a display15, configured for displaying a measured flowrate and other fluidrelated data, is mounted. A socket connector 155 and a set of diodes 156configured for infra-red communications are also provide on an upperside of the PCB.

Referring to FIGS. 7 and 8, the lower side of the PCB contains thesurface mounted devices (SMDs), such as the piezoelectric ultrasonictransducers 14 and the processor 135, and the upper side of the PCBcontains through hole components mounted by a selective solderingprocess. The upper side components, including the display, are providedwith pins 151 which are arranged in through holes in the printed circuitboard and selective soldered on the lower side of the PCB. By mountingSMDs on one side only, an effective and reliable manufacturing processmay be achieved. Additionally, by mounting the through hole componentson the upper side 132 and soldering these on the lower side, themanufacturing process may be further improved. However, the selectivesoldering process associated with the through hole components requires acertain spacing between SMDs and areas of the PCB in which selectivesoldering is used.

The flowmeter shown in FIG. 1a-1c further includes two battery packs 16for powering flowmeter operations including the processor, the metercircuit and the display. In alternative embodiments fewer or morebattery packs may also be used. To effectuate a compact and handy designsuitable for automated mass production, the battery packs are mounteddirectly on the PCB by battery pins 161 extending through plated throughholes 161 a in the PCB as shown in FIG. 3b and FIG. 4. The battery pinsare compliant pins that are deformed upon insertion into the platedthrough holes. The deformation of the battery pins ensure the necessaryelectrical contact between the pin and the PCB copper traces and securesthe battery pact to the PCB. In the shown embodiment, the battery cells162 are mounted in battery holders 163 including the battery pins.However, in alternative embodiments the battery pins may be fixeddirectly to the poles of the battery cells, e.g. by welding. Each of thebattery holders comprises a rigid element 164 provided with two batterypins in opposite ends. A battery cell may be fixated between the pins asa sub-assembly, which subsequently can be mounted on a PCB.

As seen from FIGS. 1a-c , the battery packs are mounted on the lowerside of the PCB and extend in a longitudinal direction of the flowmeteralong the flow tube. With the PCB mounted in the housing, the batterypacks are arranged on opposite sides of the flow tube providing acompact design. By arranging the batteries underneath the PCB, the spaceinside the housing is fully utilized. Further, the batteries aresupported on a bottom face of the housing thereby maintaining thebattery pins in the plated through holes 161 a.

The ultrasonic flowmeter further comprising a radio communication device18 mounted on the lower side of the printed circuit board. The radiocommunication device is connected to a radio circuit implemented on thePCB. Via the radio circuit the communication device is electricallycoupled to an antenna element 181 as will be further explained below.The radio communication device serves to transmit meter data via radiofrequency communication to a back end- or head end system (HES) whereinmeter data is stored and processed, such as for billing purposes. Theradio communication device may provide both one-way and two-waycommunication between the flowmeter and head end system. Automated meterreading (AMR) advanced meter infrastructure (AMI) systems are commonlyknown for communicating with utility meters. In an AMI a communicationpath is established between the utility meter and the HES via a numberof intermediate network devices such as data collectors, repeaters,routers gateways etc. The utility meters may deliver any data obtainedby the meter or external sensors connected to it to the HES, however thecapacity of the AMI and the battery capacity of the utility meters Mwill limit the amount of data that can be transmitted. The AMI may useany suitable technology for carrying data from the utility meter to theHES over one or more local area networks or wide area networks includingconnections to the open internet. The AMI may use any suitable wirelesstechnology (e.g. wireless M-Bus, Narrow band IoT, SigFox, any cellulartechnologies or proprietary communication protocols) or any wiredcommunication technologies (e.g. wired M-Bus, LON, Ethernet).

Still referring to FIG. 1a -1 c, a container 17 is provided on top ofthe PCB. The container comprises a compartment for containing adesiccant and the front plate 171 constitutes a lid for the container asseen from FIGS. 5 and 6. The desiccant ensures that moisture penetratinginto the flowmeter housing, such as water molecules penetrating throughits wall, are absorbed and thus does not negatively affect componentsarranged in the housing. The container further serves to protect orshield the PCB and components mounted thereon. As seen, only the displayand diodes are visible as these are received in through-going openings172, 173 provided in the container and the front plate. In analternative embodiment no components or only the display may be receivedin openings in the container.

As seen from FIGS. 3a and 5, the container further includes an antennaelement 181 mounted on its circumferential side face. In the shownembodiment, the antenna element is a piece of conducting material, suchas a stamped out piece of metal, shaped to follow the outer contour ofthe container. In an alternative embodiment, the antenna element couldbe a patch antenna or a trace deposited directly on the side of thecontainer. The antenna element 181 is connected to the radio circuit onthe PCB via connectors 183. The connectors engage with mating connectorsurfaces 184 arranged on the PCB, seen in FIG. 4.

The container and antenna element thus constitute an independentsubassembly that may be manufactured and mounted in the housing duringthe final assembly of the flowmeter. Arranging the container on top ofthe PCB serves to protect the PCB and components mounted thereon.Further, a compact design is achieved as the container is designed toencompass components extending from the PCB. Also, the container servesto position the front plate 10-40 mm above the printed circuit board.

The radio communication device is configured to detect whether anelectrical connection exists between the antenna element and itsconnectors 183 and the radio circuit. Based on input from the radiocommunication device, the meter processor 135 may thus determine whetherthe antenna element is connected to the radio circuit. Based on thisdetermination, the processor may determine whether the containerincluding the antenna element is properly mounted on top of the PCB orwhether the container has been lifted above the PCB. Lifting of thecontainer, i.e. disconnection of the antenna element, may indicate atampering event or other unauthorized access to the meter electronics.If the processor determines that the antenna has been disconnected, theprocessor may store the event in a logger of the flowmeter andeffectuate transmission, via the radio communication device, of an alarmor other information indicating a that a potential tampering event hastaken place. The container subassembly thus also serves as a tamperdetecting element designed to protect meter electronics and to warnabout possible tampering.

As described above with reference to FIG. 1c , a lower side 141 of theultrasonic transducers are arranged against an outer surface of the flowtube 11. The area of the flow tube receiving the transducers may bededicated transducer areas wherein the thickness of the flow tube may becontrolled to match the characteristics of the transducers. Inalternative embodiments wherein the flowmeter housing constituted by aseparate entity mounted on a flow tube (not shown), the transducers maybe arranged against transducer areas provided on an upper or insidesurface of a bottom part of the flow meter housing arranged to be incontact with a flowing medium in the flow tube, i.e. constituting partof the flow tube.

Referring to FIG. 2 and FIG. 4, backing devices 19 are arranged on thePCB opposite the transducers. The backing devices are arranged toprovide a holding force to the area of the PCB containing the ultrasonictransducers, thereby pressing the lower side of the transducers againstthe transducer areas, i.e. the flow tube. In FIG. 2, only one of twobacking devices is shown to illustrate how the backing devices aremounted on mounting structures 125 extending from and integrated withthe flow tube. By mounting the backing device directly to the flow tube,sufficient holding force may be obtained to keep the transducers inplace for the duration of the lifetime of the meter. Each of the backingdevices comprises a bracket element 192 fixed to the mounting structuresand spring biased backing element 191 movable in a bore of the bracketelement. A helical spring 193 is retained between the bracket elementand the backing element providing the holding force. In the shownembodiment, the bracket element is fixed to the flow tube by screws butother fixing means may also be used, such as snap-mechanisms, etc.

Alternatively, the backing devices may be comprised by a resilientmember secured to the mounting structure and an associated backingelement abutting the printed circuit board. The resilient member may bea leaf spring or a piece of polymer or rubber material having a certainresilience.

Furthermore, a lower side of the ultrasonic transducers are secured tothe transducer areas by a non-hardening adhesive, such as a butylcontaining adhesive. The adhesive connects the transducers to the flowtube thereby improving the transfer of vibrations between thetransducers and a fluid in the flow bore. The combined use of a backingdevice and a non-hardening adhesive ensure a durable constructionwherein sufficient contact between the transducers and the flow tube ismaintained for extended periods of operation. Good vibration- or signaltransfer between the transducers and the fluid is important for thesignal quality and may thus affect flow measurements.

As seen from FIG. 7 and FIG. 8 the ultrasonic transducers mayadditionally be mounted on displaceable islands 133 provided in theprinted circuit board. The islands are connected with the remainingprinted circuit board via tongues 134 of PCB containing providing acertain resilience. Hereby the part of the PCB containing thetransducers may be displaced towards the flow tube to ensure goodcontact between the flow tube and the transducers. The resilienceprovided by the tongues also isolates the reminder of the PCB fromtransducer vibrations. Further, copper traces are provided on the PCBtongues to connect the transducers to the remaining meter circuit.

Although the present invention has been described in connection with thespecified embodiments, it should not be construed as being in any waylimited to the presented examples. The scope of the present invention isset out by the accompanying claim set. In the context of the claims, theterms “comprising” or “comprises” do not exclude other possible elementsor steps. Also, the mentioning of references such as “a” or “an” etc.should not be construed as excluding a plurality. The use of referencesigns in the claims with respect to elements indicated in the figuresshall also not be construed as limiting the scope of the invention.Furthermore, individual features mentioned in different claims, maypossibly be advantageously combined, and the mentioning of thesefeatures in different claims does not exclude that a combination offeatures is not possible and advantageous.

1. A compact ultrasonic flowmeter for measuring flowrate and other fluid related data of a fluid, comprising: a flow tube with a flow bore for passage of the fluid between an inlet and an outlet; a flowmeter housing associated with the flow tube; a printed circuit board arranged in the flowmeter housing and including a processor for controlling operations of the flowmeter, a meter circuit including two or more ultrasonic transducers provided on the printed circuit board and configured for operating the two or more ultrasonic transducers to transmit and receive ultrasonic wave packets through the fluid; a display mounted on the printed circuit board and configured for displaying a measured flowrate and the other fluid related data, the processor and the two or more ultrasonic transducers being surface mounted on a lower side of the printed circuit board and the display being mounted on an upper side of the printed circuit board; one or more battery packs for powering flowmeter operations including at least the processor and the meter circuit and the display; and two or more backing devices arranged to provide a holding force to each of the two or more ultrasonic transducers, forcing a lower side of the two or more ultrasonic transducers against transducer areas provided on the flow tube.
 2. The compact ultrasonic flowmeter according to claim 1, wherein the printed circuit board includes only a single printed circuit board.
 3. The compact ultrasonic flowmeter according to claim 1, wherein the flowmeter housing is integrated with the flow tube.
 4. The compact ultrasonic flowmeter according to claim 1, wherein the two or more backing devices are mounted on top of the printed circuit board to apply the holding force to an area of the printed circuit board containing the two or more ultrasonic transducers.
 5. The compact ultrasonic flowmeter according to claim 1, wherein each of the two or more backing devices comprise a backing element abutting a corresponding one of the two or more ultrasonic transducers and/or the printed circuit board.
 6. The compact ultrasonic flowmeter according to claim 5 further comprising a restrained resilient member configured to provide the holding force.
 7. The compact ultrasonic flowmeter according to claim 6, wherein the restrained resilient member is a helical spring.
 8. The compact ultrasonic flowmeter according to claim 6, wherein each of the two or more backing devices includes a bracket element arranged to displaceably receive the backing element and the resilient member.
 9. The compact ultrasonic flowmeter according to claim 8, wherein the backing element is axially movable in a bore of the bracket element.
 10. The compact ultrasonic flowmeter according to claim 8, wherein the bracket element is fixed to the flow tube.
 11. The compact ultrasonic flowmeter according to claim 10, wherein the restrained resilient member is retained between the bracket element and the backing element.
 12. The compact ultrasonic flowmeter according to claim 1, wherein the two or more backing devices are mounted directly to the flow tube.
 13. The compact ultrasonic flowmeter according to claim 1, wherein the lower side of the two or more ultrasonic transducers are secured to the transducer areas by a non-hardening adhesive.
 14. The compact ultrasonic flowmeter according to claim 13, wherein the non-hardening adhesive is a butyl containing adhesive.
 15. The compact ultrasonic flowmeter according to claim 1, wherein the two or more ultrasonic transducers are mounted on islands provided in the printed circuit board, the islands being connected with the printed circuit board via tongues of the printed circuit board containing copper traces for electrically connecting the two or more ultrasonic transducers to the meter circuit.
 16. The compact ultrasonic flowmeter according to claim 1, wherein each of the two or more backing devices is mounted on a mounting structure that extends from the flow tube and is integrated with the flow tube.
 17. The compact ultrasonic flowmeter according to claim 16, wherein each of the two or more backing devices comprises a resilient member secured to the mounting structure, and an associated backing element abutting the printed circuit board.
 18. The compact ultrasonic flowmeter according to claim 17, wherein the resilient member is a leaf spring or a piece of polymer or rubber material having a predetermined resilience. 